1. Field of the Invention
The present invention relates to optical probes and optical methods, some embodiments thereof being particularly related to optical probes and methods having utility in the examination of material, especially material in the interior of cavities having restricted access through orifices or passageways, and some embodiments thereof being particularly related to optical probes and methods having utility in the examination of the epithelia and other tissues of anatomical structures within the body cavities and tubular organs and viscera of mammals.
2. Description of Related Art
Various apparatus are known for optically probing the interior of cavities of living and non-living bodies. An early inspection apparatus that uses a disposable sheath and which has particular application to the human cervix is described in U.S. Pat. No. 3,945,371 entitled xe2x80x9cApparatus for Inspection and Sampling in Restricted Aperture Cavities Employing Fibre Optics,xe2x80x9d issued Mar. 23, 1976 to Adelman. The disposable sheath has an upper duct terminating in a protective window for containing either one fiber optic bundle or two fiber optic bundles used in illuminating tissue and collecting a reflected image from the tissue. The light source is a lamp mounted in a reflector that concentrates the light on the end of the fiber optic bundle being used for illumination. By selecting the numerical aperture, or NA, of the fiber materials used in the image collecting fiber optics bundle, different capabilities are achieved. Fiber materials having an NA of 0.56 permit close inspection of the tissues at a viewing distance of 3 mm with low illumination, while fiber materials having an NA of 0.099 permit a general vantage at a viewing distance of 2 cm with high illumination. The possibility of using lenses is mentioned but not elaborated on.
More recently, an optical probe for use in the diagnosis of the tissues of the human cervix using fluorescence and Raman spectroscopies has been described in U.S. Pat. No. 5,697,373 entitled xe2x80x9cOptical Method and Apparatus for the Diagnosis of Cervical is Precancers using Raman and Fluorescence Spectroscopies,xe2x80x9d issued Dec. 16, 1997 to Richards-Kortum et al. The probe, which includes 2 excitation fibers and 5 collection fibers, is a type know as xe2x80x9cmulti-point contactxe2x80x9d because it uses discrete collection fibers disposed a substantially fixed distance from the tissue surface to detect fluorescence and/or Raman emissions from tissue regions proximate the distal fiber ends. The fixed distance is maintained by a quartz shield or window which contacts the tissue under investigation. The probe is part of a diagnostic or screening system that includes electromagnetic sources for generating the excitation energy, filters or spectrum analyzers for isolating wavelengths of interest, and computers for processing the wavelengths of interest to determine the tissue properties of interest. Another optical probe using a large number of paired excitation/collection fibers and a shaped contact window is described in U.S. Pat. No. 5,699,795 entitled xe2x80x9cOptical Probe for the Detection of Cervical Neoplasia Using Fluorescence Spectroscopy and Apparatus Incorporating Same,xe2x80x9d issued Dec. 23, 1997 to Richards-Kortum et al. One embodiment uses 31 fiber optic pairs in a bundle while another embodiment uses 357 fiber optic pairs in a bundle.
One disadvantage of the multi-point contact probe is its shallow depth of field, which generally necessitates that the ends of the collection fibers in the distal end of the probe be positioned a short fixed distance from the target. If any portion of the distal end of the contact probe were not properly positioned, the light energy returning from the target would not be accurately detected due to the critical depth-of-field properties of such a probe. Improper positioning of a contact probe can result from operator error or from a target that is angled with respect to the contact probe""s distal end to such an extent that full contact cannot be achieved. Another disadvantage of the multi-point contact probe is its limited resolution, which is a practical result of the difficulty and expense of assembling a large number of very fine fibers into a small probe. Yet another disadvantage of the multi-point contact probe is the lack of uniform excitation and collection of emissions due to the necessary spacing-apart of the excitation fibers and the collection fibers at the distal end of the probe.
Optical devices using lenses avoid some of the disadvantages of point contact optical probes in that they typically have better depth-of-field and better resolution. However, achieving uniform light illumination has remained problematic. Many endoscopes have offset illuminating and observing optical systems and suffer uneven illumination produced by the parallax inherent in the offset arrangement. Some endoscopes have coaxially arranged illuminating and observing optical systems to eliminate the non-uniformity introduced by parallax. For example, European Patent Specification number 0 343 558 B1, published Oct. 12, 1994 and entitled xe2x80x9cImage Picking-Up and Processing Apparatusxe2x80x9d describes an endoscope having an optical fiber bundle arranged such that its end surface surrounds an objective lens used to detect reflected light. However, the illumination achieved by this ring of discrete optical fibers is not uniform. Another type of endoscope described in U.S. Pat. No. 4,671,630 entitled xe2x80x9cIlluminating Optical System for Endoscopes,xe2x80x9d which issued Jun. 9, 1987 to Takahashi, also has coaxially arranged illuminating and observing optical systems to eliminate the non-uniform illumination introduced by parallax. To overcome the non-uniformity of earlier coaxially-arranged illuminating and observing optical systems, Takahashi uses a rectangular parallelopipedal transparent body or prism in front of the objective lens of the observing optical system and introduces light from the side of the prism. Except where the illumination enters, the sides of the prism are reflecting surfaces. Illumination light introduced into the prism is totally reflected on the objective surface due to the difference in the refractive indices of the prism and air and is also totally reflected by the reflecting side surfaces of the prism, but projects out of the object surface due to the higher refractive index of water relative to air in the tissue against which the prism is pressed during normal use. The object surface is thereby directionally illuminated, nearly obliquely so, which exaggerates shadows from irregularities in the tissue and permits a strong stereoscopic image to be achieved. While this type of illumination may be useful for observation by reflected light, its usefulness for observations based on light interactions with tissue other than reflectance is not described. Another type of endoscope described in U.S. Pat. No. 5,700,236 entitled xe2x80x9cEndoscope Attachment for Changing Angle of View,xe2x80x9d which issued Dec. 23, 1997 to Sauer et al., uses a sheath having a distal portion that contains structure for changing the angle of view and/or illumination angle of an endoscope. Structure for changing the view angle include a prism, and structure for changing the illumination angle include a prism, a curved light guide, and an angled optical fiber. However, the illumination achieved by the discrete optical fibers is not uniform for typical light interaction analysis. No measures are described for achieving uniform light using the alternative techniques.
A need, therefore, exists for apparatus and methods of providing uniform irradiation for observation involving light interactions with tissue other than reflectance or in addition to reflectance. For example, while diagonal illumination as described in the aforementioned Takahashi patent may be suitable for use with optical systems that observe reflected light, it is not effective for use with optical systems that are designed to observe light coming from within a target. For example, the aforementioned Richards-Kortum ""373 patent describes systems based on cell fluorescence and/or Raman scattered light, both of which are attributable to light that emanates from within tissue cells and not light reflected from the tissue surface. Optical systems having parallax or producing non-uniform or highly angled light relative to the target surface are not optimal for fluorescence and Raman-based systems, which require uniform diffuse light irradiation capable of penetrating into the target for quantitative or qualitative analysis.
Accordingly, an object of the present invention in various of its embodiments is to front-irradiate target materials with light that is uniform and diffuse with many near-normal rays relative to the general orientation of the target surface, throughout a field of view of the light detection system.
Another object of the present invention, in various of its embodiments, is to provide an irradiation system that uses a separate optical probe section, whether reusable, disposable, or single use, to contact target materials. Some components of the irradiation system are incorporated into the separate section of the optical probe while other components of the light delivery system are incorporated into a reusable section of the optical probe.
Another object of the present invention, in various of its embodiments, is to incorporate only low cost components of an irradiation system into a disposable or single-use section of the optical probe, while other components of the irradiation system, including high cost components, are incorporated into the reusable section of the optical probe.
These and other objects are achieved in various embodiments of the present invention. One embodiment of the present invention is an optical probe having a distally disposed optical window, comprising a light collector, a light source, and a spatial mixer. The light collector has an axis of light collection passing through the optical window and a focal plane generally proximate the optical window. The light source has a light projection pattern about the axis of light collection. The spatial mixer has a proximal end in optical communication with the light source, a distal end in optical communication with the optical window, and an axis of light projection passing through the optical window. The spatial mixer also has a light mixing surface that is partially intersected by the light projection pattern of the light source to establish a distribution of irradiation ray angles proximate the optical window that has a maximum away from normal and near-normal to the axis of light projection. In a variation thereof, the light mixing surface is partially intersected by the light projection pattern of the light source to establish a distribution of irradiation ray angles proximate the optical window that has a maximum near-parallel to the axis of light projection.
Another embodiment of the present invention is an optical probe for examining, through an optical window therein, living tissue in the interior of cavities having restricted access through orifices or passageways, comprising a body, a lens system, a light source, and an elongated inside surface. The body has an elongated distal section containing the optical window, and a proximal section. The lens system is mounted in the body and has an optical axis passing through the optical window of the probe and a focal plane lying generally proximate to the optical window. The light source is mounted in the body about the lens system and is coaxial with the lens system with a direction of light projection generally toward the optical window. The elongated inside surface has one end disposed generally about the light source and another end disposed generally about the optical window, the inside surface comprising a light scattering surface and the light projection at least partially intersecting the light scattering surface to establish a distribution of ray angles proximate the optical window that has a maximum near-parallel to the optical axis of the lens system.
A further embodiment of the present invention is an optical probe having a distally disposed optical window and comprising a light collector, a light source, and a spatial mixer. The light collector has an axis of light collection passing through the optical window and a focal plane generally proximate the optical window. The light source has a plurality of light emitting areas disposed about the axis of light collection. The spatial mixer has a proximal end in optical communication with the light source and a distal end in optical communication with the optical window to establish a direction of light projection generally toward the optical window and generally along at least part of the axis of light collection, the spatial mixer further having a light mixing surface at least partially intersected by rays of light from the light emitting areas to establish a diffuse light proximate the optical window having a distribution of irradiation ray angles that has a maximum away from normal and near-normal to the direction of light projection. In yet a further embodiment, the rays of light from the light source that intersect the light mixing surface establish, along with direct rays of light from the light source, a diffuse light proximate the optical window having a distribution of ray angles that has a maximum near-parallel to the direction of light projection.
Yet another embodiment of the present invention is a disposable for an optical probe, the disposable having a distal end to contact a target having a fluid associated therewith and a proximal end to mount to a reusable optical probe section. The disposable comprises a body having a mounting surface toward the proximal end and a light mixing inside surface toward the distal end, and an optical window element disposed within the body. The optical window element and the body proximal of the optical window element are barriers to the fluid.
Another embodiment of the present invention is a disposable for an optical probe, the disposable having a distal end to contact a target having a fluid associated therewith and a proximal end to mount to a reusable optical probe section, the disposable comprising a body, an optical element, and a reusable optical probe section connector. The body has an inside surface bounding an interior space extending between the proximal end and the distal end, the inside surface comprising at least in part a light mixing surface. The optical element is disposed across the interior space, the optical element and the body at least proximal of the optical element being barriers to the fluid. The reusable optical probe section connector is integrated with the body.
Another embodiment of the present invention is a disposable for an optical probe, the disposable having a distal end to contact a target having a fluid associated therewith and a proximal end to mount to a reusable optical probe section, the disposable comprising a tubular plastic body, an optical element, and a reusable optical probe section connector. The tubular plastic body has an inside surface bounding an interior space extending between the proximal end and the distal end, the inside surface comprising at least in part a light mixing surface. The optical element is disposed across the interior space, the optical element and the body being barriers to the fluid. The reusable optical probe section connector is integrated with the body.